prop change question

[dsujen]

I have a 1986 110hp evinrude vro mod.#e11omlcdc ser.# r1308421.with a 13x19 prop mounted on a 18ft. cobia center console. The boat peels out every once in a while usually when I floor it or in choppy water.The motor is the right height on the transome and I have the trim set right. It has no power trim. I have the thrust pin in the second hole closest to the transome. If I trim it all the way in I think the boat might dive under water once it's on plane. I marked the prop in three places: the rubber part, the metal housing and the washer before the castle nut. Took the boat out and it peeled out(reved up and didn't go no where) once in calm water. Got out and checked my marks the two on the rubber and metal housing lined up but the washer mark moved quite a bit. The prop is pretty banged up and old looking. I'm thinking the rubber inside is bad and it spins where it shouldn't. I have a new prop but it is a 14x17. The suspect prop is a 13x19 and when it doesn't slip the boat runs great.It goes 40mph into the wind and gets there fast. Doesn't sound like it over revs. I want to try the new prop but I don't have a tach to make sure it's right. Will I do damage by just putting this new 14x17 prop on and trying it? I'm assuming it is going to make the engine lug a little and get more top speed and less acceleration not sure though. The engine was tuned up by a mechanic buddy of mine and it runs great. Doesn't sound like it's over reving. Is there a rev limiter on this engine? Should I just get a new prop the same as the old one? How do I know what prop belongs on this motor and boat set up with out a tach?

 

[Mod2]

Re: prop change question

Moving to Prop Topics and Questions.

 

[Texasmark]

Re: prop change question

Lots of unanswered questions:<br /><br />Type of old and new prop<br /><br />Knowing WOT ballpark revs would help.<br /><br />Boat type, weight, and all.<br />-----------------<br />Larger diameter and shallower pitch improves heavier load handling, hole shot, not top speed....that's the direction you'd be headed.<br /><br />The 1" larger diameter would help to negate the increased rpm's caused by the reduced pitch and might bring back some of the mph loss by grabbing more water and reducing prop slippage.<br /><br />I ran a 13x17 OMC SS, as I recall, back in the '70's on a 18' trihull (Caravelle) with no tach and no trim. Engine was a 125 Johnny. I propped out to pull ski's primarily but at that I could get 39 out of the rig with me in it. Was I overrevving? I don't know. <br /><br />I started with different pitched aluminum and after tearing up several, I used that data and what I was told about the performance difference of SS to buy the 17" which I felt would be the best size for what I wanted to do. My engine purred like a kitten so if I was overrevving, I couldn't tell it.<br /><br />If you are a gambler, try it. You really aren't changing that much to make a drastic difference in the load on your engine and who knows, you might like it. It definitely would do better for you in rough seas where you are trying to hold the boat at a lower speed and battle wave action.<br /><br />My 2c<br /><br />Mark

 

[dsujen]

Re: prop change question

the new prop is a 14x17 3 blade bombardier painted aluminium prop for evinrudes i think 70-140hp. the one that i'm currently using is a beat up painted aluminum 3 blade 13x19. The boat weighs around a ton I'm guessing. It's a 1984 cobia light duty center console rated for 6 persons and 125hp. Light duty cause it has no double side walls and has low sides. How hard is it to put a tach on. If I have to I will but I'm trying to keep this boat with the least amount of electronics and do dads on it cause the salt water destroys everything. Less is more when trouble shooting in the bay when something malfuntions. In the old days like the 70's and 80's lots of boats had no tachs on em. How did these folks no what props to use?

 

[Texasmark]

Re: prop change question

I'd put the 17 on and run it. It's not going to lug if you didn't lug with the original. It would only overrev and if it is you can probably detect it by ear.<br /><br />I have run to 7500 rpm's on an engine rated for 5500 (current boat) and you can definitely tell, in coming back down to where you belong, that the engine is happy (happier)at 5500. You can tell even at 300 rpm's higher.<br /><br />Mark

 

[dsujen]

Re: prop change question

will give her a try maybe this weekend

 

[clemsonfor]

Re: prop change question

If your boat has no inner liner and is 18 ft there is no way it weighs a ton unless your standing ankle deep in water. i would guess it in the 1000lb range<br /><br />-nate